code: def __init__(self, params):
      # kfold is default validation technique
      self.validation_type = params.get("validation_type", "kfold")
  
      if self.validation_type == "kfold":
          self.validator = KFoldValidator(params)
      elif self.validation_type == "split":
          self.validator = SplitValidator(params)
      elif self.validation_type == "custom":
          self.validator = CustomValidator(params)
      else:
          raise AutoMLException(
              f"The validation type ({self.validation_type}) is not implemented."
          )
  
file_path: mljar-supervised/supervised/validation/validation_step.py
imports: import logging
  from supervised.exceptions import AutoMLException
  from supervised.validation.validator_custom import CustomValidator
  from supervised.validation.validator_kfold import KFoldValidator
  from supervised.validation.validator_split import SplitValidator
label_desc: Use image node_id 1 to create a new ValidationStep object  with example: obj = ValidationStep(params)